Theoretical treatment of internal shunt protection for superconducting magnets

Abstract

Considers the theory of internal protective shunts and switches used to limit the maximum temperature rise when a large high-current density superconducting magnet quenches, whilst operating in the persistent mode. The shunts can induce more even heating and dissipation, thus avoiding hotspots. The velocity of propagation of a normal spot in a composite superconductor is derived and its variation calculated for a particular conductor example. This is used to compute heat generation, temperature, resistivity and resistance increases and current decay and voltage characteristics for an example coil, in order to determine the minimum number of shunts required to limit the maximum temperature rise to an acceptable value.